1,928 research outputs found

    The Deterministic Capacity of Relay Networks with Relay Private Messages

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    We study the capacity region of a deterministic 4-node network, where 3 nodes can only communicate via the fourth one. However, the fourth node is not merely a relay since it can exchange private messages with all other nodes. This situation resembles the case where a base station relays messages between users and delivers messages between the backbone system and the users. We assume an asymmetric scenario where the channel between any two nodes is not reciprocal. First, an upper bound on the capacity region is obtained based on the notion of single sided genie. Subsequently, we construct an achievable scheme that achieves this upper bound using a superposition of broadcasting node 4 messages and an achievable "detour" scheme for a reduced 3-user relay network.Comment: 3 figures, accepted at ITW 201

    The Impact of Stealthy Attacks on Smart Grid Performance: Tradeoffs and Implications

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    The smart grid is envisioned to significantly enhance the efficiency of energy consumption, by utilizing two-way communication channels between consumers and operators. For example, operators can opportunistically leverage the delay tolerance of energy demands in order to balance the energy load over time, and hence, reduce the total operational cost. This opportunity, however, comes with security threats, as the grid becomes more vulnerable to cyber-attacks. In this paper, we study the impact of such malicious cyber-attacks on the energy efficiency of the grid in a simplified setup. More precisely, we consider a simple model where the energy demands of the smart grid consumers are intercepted and altered by an active attacker before they arrive at the operator, who is equipped with limited intrusion detection capabilities. We formulate the resulting optimization problems faced by the operator and the attacker and propose several scheduling and attack strategies for both parties. Interestingly, our results show that, as opposed to facilitating cost reduction in the smart grid, increasing the delay tolerance of the energy demands potentially allows the attacker to force increased costs on the system. This highlights the need for carefully constructed and robust intrusion detection mechanisms at the operator.Comment: Technical report - this work was accepted to IEEE Transactions on Control of Network Systems, 2016. arXiv admin note: substantial text overlap with arXiv:1209.176

    Oil Demand, Supply, andMedium-Term Price Prospects:A Wavelets-Based Analysis

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    The global “great recession” was precipitated in part by record high prices of oil and other commodities. Previous severe recessions have typically resulted in significantly lower energy prices, which in turn spurred growth and fueled a healthy recovery. In part due to expansionary monetary policies worldwide, oil prices have remained relatively high, making it difficult for the global economy to stage a strong recovery. The result is a short-to-medium term forecast of weak to modest growth, which – combined with continuously falling energyintensity of GDP – means that oil demand will remain stagnant or at best grow modestly. Under these circumstances, surging supply from U.S. shale and similar technologically-driven unconventional oil sources is likely to create excess supply and put strong downward pressure on oil prices. Voluntary reduction in oil production to prevent falling prices is highly unlikely, because swing producer Saudi Arabia and other GCC countries need revenues at the level of current volumes and prices in order to meet core budgetary requirements and prevent regime-change risk in the aftermath of “Arab Spring” revolts. Our wavelet analysis of all countries that have ever produced more than one million barrels of oil per day shows that regime change by itself would not result in significant reduction in oil production – although it may result in lower investment and therefore prevention of further increase in production capacity. However, war that destroys physical installations for the production and/or transport of oil can significantly disrupt oil supplies. In sum, if the outright war scenario is excluded, we expect prices to fall precipitously in the medium term (3-5 years). However, the continued threat of currently-contained civil wars into larger confrontations can maintain the current prices, especially if unprecedented monetary easing continues

    Physical, Chemical, and biotic influences on Zooplankton Composition in Zaranik Lagoon, Egypt

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    EnZaranik Protected Area encompasses the eastern end of Lake Bardawil: the Zaranik Lagoon. The lagoon is shallow, with numerous small islets scattered throughout it, most of which are covered with dense saltmarsh vegetation. Nitrogenous and phosphorus forms (ammonia, nitrite, nitrate, orthophosphate and total phosphorus) were studied as a basic nutrient salts affected different flora and fauna of the studied area. Nitrite was depleted completely during the study period except for winter. The nitrate values were fluctuated in a relatively narrow range (23.5 – 60 µg/l). Ammonia was detected in a normal range varied between 89-172 µg/l. Both orthophosphate and total phosphorus exhibit similar distribution dynamics. A total of 45 zooplankton species belonging to 9 main groups (Protista, Copepoda, Rotifera, Cladocera, Pteropoda, Cheatognatha, Cnidaria, Appendiculariae, and meroplankton) were recorded. Copepoda were the most abundant and ubiquitous zooplankton organisms in Zaranik protectorate, forming the 63 % of total zooplankton density. Salinity showed a negative correlation with total Protista (r = - 0.77) while NH3 showed a positive correlation with total zooplankton (r = 0.68)

    PLGA NANOPARTICLES LOADED MUCOADHESIVE AND THERMOSENSITIVE HYDROGEL AS A POTENTIAL PLATFORM FOR THE TREATMENT OF ORAL MUCOSITIS

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    Objective: The objective of this study was to design an effective topical treatment for oral mucositis.Methods: Poly-(DL-lactide-co-glycolide) (PLGA) nanoparticles (NPs) and Poloxamer407 (PLX)/Hydroxy propyl methyl cellulose (HPMC) hydrogel matrix (HG) were used as combined carriers for benzydamine HCL (BNZ). BNZ loaded PLGA nanoparticles were assessed for their particle size, PDI, zeta potential and entrapment efficiency. Scanning electron microscopy, thermosensitivity study, mucoadhesion study, in vitro release and in vivo investigation were used to characterize the combined BZN loaded PLGA NPs HG.Results: Negatively charged NPs with an average diameter of 139±4.92 nm were incorporated into PLX/HPMC HG bases. The gelation temperature of BZN-PLGA-NPs-HGs ranged between 31°C and 36.5°C. When diluted with saliva simulated fluid, BZN-PLGA-NPs-HGs preserved their gelation properties. Mucoadhesion was found lower for formulations prepared with PLX without HPMC. An increase in the concentrations of PLX from 10 to 30% resulted in an increase in adhesion. Both PLGA-NPs and PLGA-NPs-HG provided a biphasic drug release profile while BZN-HG provided monophasic zero order release pattern. The in vivo study showed that animal groups treated with BZN-HG and BZN-PLGA-NPs-HG showed a significantly higher reduction percentage in ulcer surface area compared to those treated with BZN-PLGA-NPs. BZN-PLGA-NPs-HG group needed 10 d of treatment to complete healing versus 16 d, 14 d and 12 d for the complete healing of groups with no treatment, treated with BZN-PLGA-NPs and treated with BZN-HG, respectively.Conclusion: BZN-PLGA-NPs-HG could represent a promising mean for the effective treatment of oral mucositis induced by cancer therapy

    The Lateral Distortional Buckling of I-Plate Girders

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    This paper presents a numerical study for lateral distortional buckling of I-plate girders (LDBIPGs) by using the general-purpose finite element package ABAQUS (version 6.13) software. 3-D finite element (FE) models for simply supported IPGs subjected to two cases of loading are built. The first case of loading was uniform end moment that was introduced by a couple of forces applied at the top and bottom flanges of the IPGs. The second case of loading was a concentrated load at the shear center in the mid-span. First, shell finite element models are validated by comparing the FE critical bending moment (������,����) by the critical bending moment in EC3 code (������,��,������). The results indicate that the ������,���� was in good agreement with ������,��,������. Secondly, a preliminary analysis is conducted to the relative girder slenderness (��) where the LDB too place. Finally, a parametric study is carried out on simply supported IPGs regarding to the span length, the flange cross-section dimensions and the thickness of the web. The results showed that increasing the length of girders decreases ������.���� and increase in the bending coefficient factor (����). Also, decreasing in the web plate slenderness ratio (��������⁄) works on increasing in ������.���� values and ����. The results also showed that the increasing in the thickness of flange increases ������.���� and increase the value of ���� with small value. As a result of parametric study, the mean value and standard deviation of ���� for LDB mode are 1.16 and 0.08 respectively for �� limits (90:130). For �� limits (131:175), the mean value and standard deviation of ���� are 1.27 and 0.03 respectively. As for �� limits (176:221), the mean value and standard deviation of ���� are 1.32 and 0.02 respectively

    Recurrent Pneumonia in Children Admitted to Assiut University Children Hospital. Magnitude of the Problem and Possible Risk Factors

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    Background: Incidence data indicate that recurrent pneumonia occurs in 7.7–9% of all children withcommunity acquired pneumonia. We aim by this study to assess the prevalence of recurrent pneumoniaamong the admissions with diagnosis of pneumonia in Assiut university children hospital for one year andto try to define the possible related risk factors. Patients and methods: This is a prospective hospital basedstudy in Assiut University Children’s Hospital. Children younger than 16 years admitted with a hospitaldiagnosis of pneumonia to Assiut University Children’s Hospital for one year from 1 February 2017 to 31January 2018 were included.Results: Approximately 1 in 12 children with pneumonia in our locality have recurrent pneumonia with percentageof 12.61%. Cardiac diseases especially congenital heart diseases was the cause among 25.45%of the cases, immunodeficiency diseases represented 20.9% of the cases ,while bronchial asthma wasthe cause of recurrent pneumonia among 16.36% of the cases. As regard to risk factors in studied group,prematurity was detected among 7.27 % of the cases while more than 50% were formula fed and more than60% exposed to pollution. Father smoking was detected among 36.36% of cases. Patients aged > 6 yearsshowed significantly higher frequency in risk factors as obesity, indoor and outdoor pollution and use ofsteroids in comparison to other age groups. However, patients aged 0-3 years exhibited significantly higher% frequency of having heart disease, oro-motor in coordination /swallowing dysfunction, gastro esophagealreflux and under nutrition as risk factors for recurrent pneumonia in comparison to other age groups.Conclusions: The most frequent underlying cause for recurrent pneumonia in Assiut University Children’sHospital which presents the largest referral pediatric hospital in Upper Egypt for one year according to ourstudy was cardiac diseases; the second most frequent cause was immunodeficiency diseases, followedby bronchial asthma. Risk factors for recurrent pneumonia include socio-economic status of studiedcases, prematurity, exposure to passive smoking and in or outdoor pollution, obesity, under nutrition, lackof breast feeding, gastro esophageal reflux and steroids usage
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